Traveling wave oscillator



June 30, 1959 E. c. DENcH 2392363 TRAVELING WAVE OSCILLATOR Original Filed Dec. 30. 1953. 2 Sheets-,Sheet 2 E DWA/2D C. DENCH TTORNEY United States Patent O TRAVELING WAVE OSCILLATOR Edward C. Dench, Needham, Mass.

Original application December 30, 1953, Serial No. 401,340, now Patent No. 2,859,380, dated November 4, 1958. Divided and this application October 7, 1955, Serial No. 539,048

20 Claims. (Cl. 315-393) This application is a division of my copending application Serial No. 401,340, filed December 30, 1953, now United States Letters Patent No. 2,859,380, issued November 4, 1958.

This invention relates to oscillating tubes of the traveling wave type which may be connected either singly or in parallel.

Linear traveling wave tubes are known which comprise an electron gun at one end of said tube, an electron collecting electrode at the other end thereof, and an elongated periodic slow wave propagating structure or delay line, such as a helix, a strapped vane network or an interdigital delay line, which is adapted to transmit high-frequency energy with a Velocity comparable to the Velocity of the electron stream and which is nonresonant Within the passband of the structure. The electrons are projected in the vicnity of the periodic delay structure so that high-frequency energy is transferred from the electron stream to the wave propagating along the periodic structure. The energy generated in such tubes may be coupled from said periodic structure by way of an output coupling means.

In order to obtain sufiicient energy interaction, such tubes are usually relatively long and, hence, require an axial magnetic field to prevent dispersion of the electron beam as it traverses the periodic structure.

If high beam currents can be mantained in a traveling wave oscillator of the type described, the gain per unit length of tube is relatively high and the length of tube necessary for effective production of oscillations may be decreased considerably. If a tube of sufficiently short length may be used, the axial focusing magnetic field may be eliminated with a consequent saving in size, weight and cost. The above conditions may be attained, in accordance with this invention, by connecting a plurality of such traveling wave oscillators in parallel. Furthermore, by connecting the output coupling means of the various traveling wave tubes in parallel, large amounts of power may be derived with comparatively low power tubes, thereby obviating the need for high-power tubes which, because of such factors as external cooling and specially designed cathodes, are relatively diflicult and expensive to realize in practice.

If an infinite number of said traveling wage oscillators were to be connected radially in shunt, a resulting cylindrical tube would be obtained comprising a continuous cathode or electron source, a centrally positioned collector electrode, and some form of radial periodic transmission line. If the periodic delay line were of the type shown in the application for United States Letters Patent of E. C. Dench, Serial No. 255,499, filed November 8, 1951, now United States Letters Patent No. 2,809,- 328, issued October 8, 1957, and consisting of a plurality of spaced vanes or paddles depending from a solid hacking member, the developed periodic structure becomes a series of coaxially arranged annular members which may depend from a wall of the tube envelope. The resulting cylindrcal tube is preferable to a linear tube inasmuch as it is more compact and symmetrical.

Cylindrical traveling wave oscillators have been developed whose operation depends upon the interaction between an electron beam and one of the space harmonics of the R.F. wave traveling along a non-reentrant periodic delay line. One such tube capable of generating high-freqency energy is shown and described in an application by E. C. Dench for United States Letters Patent, Serial No. 357,824, filed May 27, 1953. This tube includes an arcuate periodic delay structure surrounding and concentrically arranged with respect to a cylindrcal negative electrode, thus forming an arcuate interaction space. A heated cathode positioned adjacent the sole serves as a source of electrons. Under the combined influence of properly adjusted crossed electric and magnetic fields, these electrons are caused to encircle the interaction space and eventually mpinge upon an electron collecting electrode.

While such tubes are quite eflicient and satisfactory in operation, they require a rather large and heavy magnet assembly in order to permit the electrons to travel in a circular path about the arcuate interaction space. It is often desirable, as in the case of airborne equipment, to reduce the size and weight of an oscillator to a minimum. Since magnets of sutficient flux density for use with high-frequency traveling wave oscillators are bulky and heavy, a cylindrcal tube capable of operation in the absence of a magnetic field is highly desirable.

Furthermore, since it is often diflicult to maintain the field strength of a permanent magnet uniform over a period of time, a traveling wave tube requiring no magnetic field will have more stable operating characteristics than one including a magnetic field producing means, all other things being equal.

In addition, where high power traveling wave tubes are required, a relatively large cathode is desirable. In prior traveling wave oscillator tubes, the cathodes have been comparatively small and limit the amount of power which the tubes are capable of supplying.

In one embodiment of traveling wave oscillator tube of the subject invention, the traveling wave tube includes an annular cathode mounted within a substantially cylindrcal envelope adjacent the circumferential wall of said envelope. The latter includes a pair of spaced end plates sealed to said wall. A collector electrode is centrally positioned within the tube envelope and serves to collect the electrons emitted from the surrounding cathode. Interposed between the cathode and the collector electrode is a periodic anode delay structure consisting of a plurality of spaced, concentrically arranged annular members depending from oppositely positioned portions of the tube envelope. The radially directed electron beam passes adjacent this periodic structure and interaction between the beam and the proper spatial harmonic of the R.F. field associated with the periodic structure results in the generation of oscillations. In order to permit the electrons leaving the cathode to obtain a substantially uniform Velocity before passing by the periodic anode structure, a positive -accelerating electrode is positioned adjacent said cathode.

An output may be derived from the traveling wave oscillator by means of an annular slot in one of the end walls of the envelope positioned between any two adjacent annular members near the cathode. Any highfrequency transmission line bounding said annular slot can be used for coupling the oscillations generated into an external load.

In another embodiment, the cathode and collector electrode are reversed from the position just described so that the cathode is located along the axis of the cylndrical envelope while the circumferential wall of the envelope becomes the electron collecting electrode.

The traveling wave oscillator tubes already described may be modified by forming the periodic anode delay line in the form of a series of concentric, annularly arranged sets of interdigital members, each set including alternately dsposed members extending, respectively, from oppositely dsposed portions of the 'tube envelope. Each set of the interdigital members overlaps the other set without extending all the way to the opposite porton of the tube envelope. To permit proper nteraction between the electron beam and the R.F. wave associated with the periodic interdigital line, the overlapping portions of the annular members contain radially-aligned apertures at various angular positions. The electrons from the cathode then pass through the various apertures as a plurality of radially-directed beams on their way to the 'collector electrode.

Since no magnetic field is required in either of the two embodiments of traveling wave oscillators of the subject invention, tubes of comparatively light weight and smaller bulk are obtainable, and undesirable efiects of variations in magnetic field strength on tube Operating characteristics are elimnated. Because of the -relativelI large cathode obtained in the embodiment having the circumferential cathode, larger amounts of power may be obtained for a given size tube than from the traveling wave oscillators of the prior art. Either of the embodiments shown is of compact, symmetrical 'construction and may be readily manufactured and reproduced.

Other and further objects and advantages of this invention will become apparent as the description thereof progresses, reference being had to the accompanying drawings wherein:

Fig. 1 is a schematic view of a parallel arrangement of traveling wave oscillator tubes;

Fig. 2 is a view showing one form of traveling wave oscillator tube embodying the subject invention;

Fig. 3 is a view showing an alternative form of traveling wave oscillator tube embodying the subject invention;

Fig. 4 is a cross-sectonal view of a modfication of the tube of Fig. 2 having an nterdgital periodic anode structure; and

Fig. 5 is a cross-sectional view of the tube of Fig. 4 taken along line 5-5 of Fig. 4.

In the various figures of the drawing, corresponding elements will be desgnated by like reference numerals.

Referring to Fig. 1, a plurality of radially-dsposed traveling wave oscillators are shown schematically, each comprising a cathode or electron source 11, au electron collecting electrode 12 and a periodic transmission delay line 14 which may, for example, be a helix. The electron beam 15 from cathode 11 interacts with the R.F. field along the periodic line 14 to generate energy which travels along the periodic line in a direction opposite to the direction of movement of the electrons. The energy is removed from the end of the periodic line remote from the collector electrode by output couplng means 17, indicated by an arrow, while the opposite end of the delay line is terminated by an electrical attenuating means, such as shown and described in the aforesaid copending application, Serial No. 357,824, and indicated schematically by the cross-hatching 19. The outputs of the tubes are connected in parallel and applied by way of any suitable transmission lines 18 to a common load 20.

Referring now to Fig. 2 the traveling wave oscillator tube 10 includes a cylindrical envelope 22 having a circumferential wall porton 23 joined to a pair of fiat, oppositely-disposed annular end plates 24 and 25. An electrically conductive collector electrode 12 is centrally located in the tube and is fixedly mounted to one end plate 25, as shown in Fig. 2. This collector electrode assases is preferably tubular in order to permt the insertion of a fiuid cooling conduit 27, although a solid collector may be used, especially in low power tubes. An annular cathode 11, indirectly heated by a suitable heater 28 wound about the periphery of the cathode, is insulatedly mounted with respect to the circumferential wall 23 of the tube envelope by means of an appropriate number of spaced support rods or wires 30. These rods may be attached to the cathode at various points around the circumference thereof, as by soldering, and brought through an aperture in wall 23 containing an electrically insulating bead 31, such as glass. The inner surface 33 of the cathode is coated with an electron-emissive material 35, in a well-known manner. Cathode 11, for reasons to be given subsequently, is preferably concave inward, as clearly shown in Fig. 2, although, in some instances, it may be planar. An external electrical connection for the cathode and heaters is provided by means of corresponding lead-in conductors 36-38 insulated from wall 23 by means of glass beads 39. A pair of focusing electrodes 40 and 41 are postioned adjacent to cathode 11. These electrodes may have the same curvature as the cathode so as to form, in effect, an extension of the cathode. In many instances, however, the inner surface of the focusing electrodes may be flat rather than convex. The focusing electrodes in practice may be maintained at a potential somewhat negative with respect to the cathode. The presence of the focusing electrodes and the concavity of the cathode-emitting surface combine not only to direct or focus the electron beam radially inward, but also to cause slght divergence of the beam as it progresses toward the collector.

A pair of accelerating electrodes 44 and 45, one adjacent each end of the cathode assembly, are mounted by support rods 47 aflixed, in the same manner as the cathode, to respective end plates 24 and 25. These accelerating electrodes are maintained positive with respect to the cathode. The electrical connections to the accelerating electrodes and focusing electrodes, like those to the cathode and heater, are made through lead-in conductors 48-51 passing through beaded apertures in the wall 23 of the tube envelope.

The periodic energy propagating means for the travelng wave tube is postioned between the electron gun assembly and the collector electrode. Because of the symmetrical construction of the tube, a pair of oppositely dsposed periodic transmission delay lines or structures 14 and 14' may be provided to enhance the nteraction between the electron beam and the periodic line. The tube may, however, operate with a single periodic structure 14. These periodic anode delay structures each comprises a plurality of coaxially arranged annular electrically conductive members or vanes 58 depending from end plates 24 and 25, respectively. These members may be attached to the appropriate portions of the tube envelope by brazng. Members 58 may be equally spaced, as shown in Fig. 2, although the invention is not so limited, inasmuch as the spacing may be progressively changed in either direction along the periodic line.

The periodic anode delay lines 14 and 14' are electrically interconnected and, being a part of the tube envelope, are obviously at the same unidirectional current potential as the tube envelope. The periodic anode may be maintained at a potential positive with respect to the cathode by means of a connection 57 attached to some point on the tube envelope. As shown in Fig. 2, collector electrode 12 is electrically a part of the periodic anode line and, therefore, is at the same unidirectional potential. Alternatively, the collector may be insulated from the periodic anode line and maintained at a potential somewhat less positive than the anode where slightly greater efliciencies are required.

Energy is taken from the tube through an annular coupling slot 60 formed in wall 24 of the tube envelope in the region between two adjacent annular members lying near the end of the periodic delay line nearest the cathode. Since this coupling slot is preferably reentrant, the portion 24' of wall 24 bounded by the slot is separate from the outer portion of the wall. In this case mechanical support for the inner portion 24' is furnished by means of the collector electrode 12 which is attached to the underside thereof. If less coupling can be tolerated, the slot may be interrupted at various points in order to permit the portion 24' of wall 24 to remain integral with the remainder of wall 24. In this way, no mechanical support need be furnished by the collector electrode. To confine the energy emanating from slot 60, an output coupling means 17 is provided in the form of a coaxial line 62, including an inner conductor 63, and outer conductor 64 is attached to the tube envelope. The outer conductor 64 is attached to wall 24 adjacent to and externally of the aperture, as shown in Fig. 2. The inner conductor 63 is fixedly attached to the inner portion 24' of wall 24. The size of the inner conductor depends upon the value of coaxial line impedance desired. To provide proper impedance matching between the traveling wave oscillator and the external load, not shown, over a wide band of Operating frequencies, the coaxial line may be tapered in a manner shown in Fig. 2. A vacuum seal is provided by means of a dielectrc head 65, such as glass, inserted within coaxial line 62, as shown in Fig. 2.

The tube shown in Fig. 3 differs essentially from that shown in Fig. 2 in that the cathode and collector electrodes are reversed so that the electron beam travels radially outward instead of toward the center of the tube. The construction of the tube of Fig. 3 is somewhat simplified inasmuch as the circumferential wall 23 of the tube envelope may serve as the electron collecting electrode. The cathode 11 is centrally mounted within the tube envelope and is preferably concave as viewed from the circumferential wall 23. The cathode contains a longitudinal aperture 13 extending part way through the cathode for receiving one end of a tubular metallic supporting member 68. The aforesaid one end of member 68 is connected, as by welding, to the inner be enlarged to provide better mechanical support, is sealed to an electrically insulating element 21 which, in turn, is secured to the end plate 25 of the tube envelope adjacent an aperture therein through which the supporting member and insulating element pass. The cathode is connected to an appropriate source of unidirectional potential by means of a lead 36 electrically connected to the enlarged end of cathode supporting member 68. The cathode heater 28 is inserted within the bore in supporting member 68 and a vacuum is maintained by means of a glass or ceramic bead 69 through which the heater wire passes. Cathode 11 may be provided with integral end shields 11' at each end thereof which serve not only to minirnize emission on the longitudinal axis of the cathode but also as support means for the focusing electrodes 40 and 41. The latter, except for size and method of mounting, are similar to those used in the tube of Fig. 2. The accelerating eleotrodes 44 and 45 are arranged adjacent to and concentric with said cathode, in like fashion to those of Fig. 2, and may be supported from the corresponding end plate 24 and 25 of the tube by electrically insulating supports 47.

Since the wave energy in the traveling wave oscillator travels in a direction opposite to that of the electron beam, a reversal of the direction of propagation of the electrons will result in energy traveling along the periodic anode network 14 toward the axis of the tube. The annular energy coupling slot 60 in end plate 24 forming a part of output coupling means 17, is, therefore, located between two adjacent annular members 58 near the center of the tube, instead of near the crcumferential wall of the tube, as in the case of Fig. 2. With the tube of Fig. 3, therefore, a smaller output coupling means may suflice than in the case of the tube of Fig. 2. This provides for a further simplification in construction of the traveling wave oscillator.

As pointed out in connection with Fig. 2, unless the apertured slot 60 in the tube of Fig. 3 is made discontinuous in order to maintain the central portion 24' of end plate 24 integral with the outer portion, mechanical support must be provided. The cathode 11 may be provided with an extension 11" which may be connected by the usual ceramic-to-metal sealing techniques to the underside of central portion 24' of the end plate.

A modification of the tube of Fig. 2 is shown in Figs. 4 and 5, in which the vane-type periodic anode delay structure has been replaced by an interdigital structure. As shown in Figs. 4 and 5, the interdigital structure comprices a first set of concentrically arranged annular members 58a afiixed to and depending from end plate 24 of the tube envelope. Attached to and extending perpendicularly from the opposite end plate 25 is a second set of coaxially arranged annular members 58h which are interspersed between the various members of said first set. The free ends of the two sets of members overlap. The overlapping regions of the members contain a number of apertures 70, depending upon the number of electron beams 15 desired. The apertures in the various members are radially aligned, as shown in Fig. 5, so that the electron beam may readily pass from cathode 11 to collector electrode 12.

The electron beam, in passing through the apertures in the overlapping members, reacts with the R.F. field associated with the periodic interdigital 'structure to produce oscillatory energy which may be coupled from the tube by output coupling means 17 including annular coupling slot 60 and a wave guide 72 whose wa'll 73 lies adjacent to and externally of the annular slot. The wave guide may be provided with a microwave window 75 which maintains a vacuum-tight seal for the tube while, at the same time, being transparent to microwave energy.

A wave guide or coaxial output line may be used alternatively as output coupling means in any of the embodiments of this invention. For example, in Fig. 4, the waveguide 72 may be removed from end plate 24 and a coaxial line of the proper size and constructed like coaxial line 62 of Fig. 3 may be mounted on end plate 24 of Fig. 4 with the outer conductor 64 attached to end plate 24 adjacent to and externally of aperture 60 in the end plate 24 of Fig. 4, while the inner conductor 63 of the coaxial line may be attached to the inner portion 24' of end plate 24 of Fig. 4. In fact, the invention is not limited to any particular type of such output deriving means.

It is, of course, possible to utilize an interdigital periodic anode structure of the type shown in Figs. 4 and 5 in a tube having a centrally positioned cathode, such as that of F ig. 3.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is, accordingly, desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. A traveling wave electron discharge device comprising an evacuated substantally cylindrical envelope, a source of electrons, an accelerating electrode and a collector electrode each concentrically mounted within said envelope, a periodic non-reentrant, non-resonant wave energy transmission structure including a plurality of coaxfially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and |said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths adjacent to and in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic structure, and means for extracting said energy traversing said periodic structure from said electron dscharge device.

2. A traveling wave electron dscharge device comprising an evacuated substantially cylindrical envelope, a source of electrons and a collector electrode each concentn'cally mounted within said envelope, a pair of oppositely disposed periodic non-reentrant, non-resonant wave energy transmission structures including a plurality of coaxially arranged annular members positioned between said electron source and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, and means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths adjacent to and in energy nteracting relationship with the electromagnetic field of wave energy propagating along said periodic structures.

3. A traveling wave electron dscharge device comprising an evacuated substantially cylindrical envelope, a source of electrons and a collector electrode each concentrically mounted within said envelope, a pair of oppositely disposed periodic non-reentrant, non-resonant wave energy transmission structures including a plurality of coaxially arranged annular members positioned between said electron source and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths adjacent to and in energy nteracting relationship with the electromagnetic field of wave energy propagating along said periodic structures, and means for extracting said energy traversing said periodic structures from said electron dscharge device.

4. A traveling wave electron dscharge device comprising an evacuated substantially cylindrical envelope, a source of electrons, an accelerating electrode and a collector electrode each concentrically mounted within said envelope, a pair of oppositely disposed periodic nonreentrant, non-resonant wave energy transmission structures including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths adjacent to and in energy nteracting relationship with the electromagnetic field of wave energy propagating along said periodic structures and in the opposite direction to the direction of travel of said wave energy, and means for extracting from the region of said periodic structure adjacent said source the energy traversing said periodic structures.

5. A traveling wave electron dscharge device comprising an evacuated substantially cylindrical envelope, a source of electrons, an accelerating electrode adjacent thereto and a collector electrode each concentrically mounted within said envelope, a pair of oppositely disposed periodic non-reentrant, non-resonant wave energy transmission structures including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths in energy nteracting relationship with the electromagnetic field of wave energy propagating along said periodic structures, and means connected to the end of one of said delay structures adjacent said source of electrons for extracting said energy traversing said periodic structures from said device.

6. A traveling wave electron dscharge device comprising an evacuated substantially cylindrical envelope, a

source of electrons, an accelerating electrode adjacent said source, and a collector electrode each concentrically mounted within said envelope, a pair of oppositely disposed periodic non-reentrant delay structures for transmission of wave energy, said structures each including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths in energy nteracting relationship With the electromagnetic field of wave energy propagating along said periodic structures and in a direction opposite to the direction of travel of said wave energy, an annular coupling slot contained in a portion of said envelope and lying between two adjacent members near the end of one of said periodic structures remote from said collector electrode, and output coupling means bounded by a Wall electrically connected to said tube envelope in the vicinity of and externally of said annular slot.

7. A traveling wave electron dscharge device comprising an evacuated substantially cylindrical envelope, a source of electrons, an accelerating electrode adjacent said source and a collector electrode each concentrically mounted within :said envelope, a pair of oppositely disposed periodic non-reentrant delay structures for transmission of wave energy, said structures each including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means .for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths in energy nteracting relationship with the electromagnetic field of wave energy propagating along said periodic structures and in a direction opposite to the direction of travel of 'said wave energy, an annular coupling slot contained in a portion of said envelope and lying between two adjacent members near the end of one of said periodic structures remote from said collector electrode, a coaxial output coupling means including an outer conductor and an inner conductor, said outer conductor being electrically connected to said tube envelope in the vicinity of and externally of said annular slot and said inner conductor being electrically connected to the portion of said tube envelope surrounded by said annular slot.

8. A traveling wave electron dscharge device comprising an evacuated substantially cylindrical envelope, a source of electrons, an accelerating electrode adjacent said source and a collector electrode each concentrically mounted within said envelope, a periodic non-reentrant delay structure for transmission of wave energy, said structure including a plurality of interdigital, coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, said interdigital members containing a group of radially aligned apertures, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source through said apertures toward said collector electrode along radial paths in energy nteracting relationship with the electromagnetic field of wave energy propagating along said periodic structures and in a direction opposite to the direction of travel of said wave energy, an annular coupling slot contaned in a portion of said envelope and lying between two adjacent members near the end of said delay structure remote from said collector electrode, and output coupling means bounded by a wall electrically connected to said tube envelope in the vicinity of and externally of said annular slot.

9. A traveling wave electron dscharge device comprisasa-2,988

ing an evacuated substantially cylindrica'l envelope, a source of electrons centrally positioned within said envelope, an accelerating electrode positioned adjacent said source for permitting said electrons to achieve a uniform Velocity, a collector electrode surrounding said source of electrons, a periodic non-reentrant, non-resonant delay structure for transmission of wave energy dependng from said envelope and including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, and means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic structure and in a direction opposite to the direction of travel of said wave energy.

10. A traveling wave electron discharge device comprising an evacuated substantially cylindrical envelope, a source of electrons centrally positioned within said envelope, an accelerating electrode positioned adjacent said source for permittng said electrons to achieve a uniform Velocity, a collector electrode surrounding said source of electrons, a pair of periodic non-reentrant, non-resonant delay structures for transmission of wave energy depending from oppositely disposed portions of said envelope and including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic structures and in a direction opposite to the direction of travel of said wave energy, and means for extracting energy traversing said periodic structures from said electron discharge device.

11. A traveling wave electron discharge device comprising an evacuated substantially cylindrical envelope, a source of electrons centrally positioned within said envelope, an accelerating electrode positioned adjacent said source for permitting said electrons to achieve a uniform Velocity, a collector electrode surrounding said source of electrons, a periodic non-reentrant, non-resonant delay structure for transmission of wave energy depending from oppositely disposed portions of said envelope, said delay structure including a plurality of interdigital, coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, said interdigital members containing a group of radially aligned apertures therein, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source through said apertures toward said collector electrode along radial paths in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic structure and in a direction opposite to the direction of travel of said wave energy, and means for extracting energy traversing said periodic delay structure from said electron discharge device.

12. A traveling wave electron discharge device comprising an evacuated substantially cy'lindrical envelope, a source of electrons positioned adjacent said envelope, an accelerating electrode disposed adjacent said source for permitting said electrons to attain a uniform Velocity, a collector electrode centrally positioned within said tube envelope, a periodic non-reentrant, non-resonant delay structure for transmission of wave energy depending from said envelope and including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, and means responsive only to said electric field for directing electrons from said source toward said collector electrode along radia'l paths in energy -interacting relationship with the electromagnetic field of wave energy propagating along said periodic structure and in a direction opposite to the direction of travel of said wave energy.

13. A traveling wave electron discharge device comprising an evacuated substantially cylindrical envelope, a source of electrons positioned adjacent said envelope, an accelerating electrode disposed adjacent said source for permitting said electrons to attain a uniform velocity, a collector electrode centrally positioned within said tube envelope, a pair of periodic non-reentrant, non-resonant delay structures for transmission of wave energy depending from oppositely disposed portions of said envelope and including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic structures and in a direction opposite to the direction of travel of said wave energy, and means for extracting energy traversing said periodic delay structures vfrom said electron discharge device.

14. A traveling wave electron discharge device comprising an evacuated substantially cylindrical envelope, a source of electrons positioned adjacent said envelope, an accelerating electrode disposed adjacent said source for permitting said electrons to attain a uniform Velocity, a collector electrode centrally positioned within said tube envelope, a periodic non-reentrant, non-resonant delay structure for transmission of wave energy depending from oppositely disposed portions of said envelope, said delay structure including a plurality of interdigital, coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, said interdigital members containing a group of radially aligned apertures therein, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source through said apertures |toward said collector electrode along radia'l paths adjacent to and in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic structure and in a direction opposite to the direction of travel of said wave energy, and means for extracting energy traversing said periodic delay structure from said electron discharge device.

15. A traveling wave electron discharge device comprising an evacuated substantially cylindrical envelope having a circumferential wall portion and a pair of end portions normal thereto, a source of electrons positioned adjacent said circumferential wall portion, an accelerating electrode disposed adjacent said source for permitting said electrons to attain a uniform velocity, a collector electrode centrally positioned within said tube envelope, a pair of oppositely disposed periodic non-reentrant delay structures for transmission of wave energy depending from corresponding ones of said end portions and including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths in energy interacting relationship with the electromagnetic field of Wave energy propagating along said periodic structures and in a direction opposite to the direction of travel of said wave energy, an annular coupling slot contaned in one of said 11 end portions and lying between two adjacent members near the end of said delay structure remote from said collector electrode, and output coupling means bounded by a Wall electrically connected to said one portion of said tube envelope in the vicinity of and externally of said annular slot.

16. A traveling wave electron discharge device comprising an evacuated substantially cylindrical envelope having a circumferential wall portion and a pair of end portions normal thereto, a source of electrons positioned adjacent said circumferential wall portion of said tube envelope, an accelerating electrode disposed adjacent said source for permitting said electrons to attain a uniform velocity, a collector electrode centrally positioned within said tube envelope, a pair of oppositely disposed periodic non-reentrant delay structures for transmission of wave energy depending from corresponding ones of said end portions and including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source to- Ward said collector electrode along radial paths in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic structures and in a direction opposite to the direction of travel of said wave energy, an annular coupling slot contained in one of said end portions and lying between two adjacent members near the end of said delay structure remote from said collector electrode, a coaxial output coupling means including an outer conductor and an inner conductor, said outer conductor being electrically connected to said tube envelope in the vicinity of and externally of said annular slot and said inner conductor being electrically connected to the portion of said tube envelope surrounded by said annular slot.

17. A traveling wave electron discharge device compri'sing an evacuated substantially cylindrical envelope having a circumferential wall portion and a pair of end portions, a source of electrons positioned adjacent said circumferential Wall portion of said tube envelope, an accelerating electrode disposed adjacent said source for permitting said electrons to attain a uniform Velocity, a collector electrode centrally positioned within said tube envelope, a periodic non-reentrant structure for transmission of wave energy including a plurality of concentrically arranged annular interdigital arrays of first and second members, said first and second members depending from opposite ones of said end portions, radially aligned apertures contained in said first and second members of said array, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing said electrons through said apertures in energy interacting relationship With the electromagnetic field of wave energy propagating along said periodic delay structure and in a direction opposite to the direction of travel of said wave energy, an annular coupling slot contained in one of said end portions of said envelope and lying between two adjacent members near the end of said delay structure remote from said collector electrode, and output coupling means bounded by a wall electrically connected to said one portion of said tube envelope in the vicinity of and externally of said annular slot.

18. A traveling wave electron discharge device comprising an evacuated substantially cylindrical envelope having a circumferential wall portion and a pair of end portions, a source of electrons centrally positioned within said envelope, an accelerating electrode disposed adjacent said source for permitting said electrons to attain a uniform Velocity, a collector electrode forming the circumferential wall portion of said tube envelope, a pair of oppositely disposed periodic non-reentrant delay structures for transmission of wave energy depending from said correspondng ones of said end portions and including a plurality of coaxially arranged annular members positioned between said accelerating electrode and said collector electrode, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along radial paths in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic structures and in a direction opposite to the direction of travel of said wave energy, an annular coupling slot contained in one of said end portions of said envelope and 'lying between two adjacent members near the end of said delay structure remote from said collector electrode, and output coupling means bounded by a wall electrically connected to said tube envelope in the vicinity of and externally of said annular slot.

19. A traveling wave electron discharge device comprising an evacuated substantially cylindrical envelope having a circumferential wall portion and a pair of end portions, a source of electrons centrally positioned within said envelope, an accelerating electrode disposed adjacent said source for permitting 'said electrons to attain a uniform Velocity, a collector electrode forming the circumferential wall portion of said tube envelope, a periodic non-reentrant structure for transmission of wave energy including a plurality of concentrica'lly arranged annular interdigital arrays of first and second members, said first and second members depending from opposite ones of said end portions, radially aligned apertures contained in said first and second members of said arrays, means for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing said electrons through said apertures in energy interacting relationship with the electromagnetic field of wave energy propagating along said periodic delay structure and in a direction opposite to the direction of travel of said wave energy, an annular coupling slot contained in one of said end portions of said envelope and lying between two adjacent members near the end of said delay structure remote from said collector electrode, and output coupling means bounded by a wall electrically connected to said tube envelope in the vicinity of and externally of said annular slot.

20. A traveling wave electron discharge device comprising a source of electrons, a collector electrode, a periodic non-reentrant, non-resonant wave energy transmission structure capable of propagating electromagnetic wave energy in more than one direction and positioned between said source and said collector electrode, means 'for producing an electric field between said source of electrons and said collector electrode, means responsive only to said electric field for directing electrons from said source toward said collector electrode along more than one path adjacent to and in energy-interacting relationship with the electromagnetic field of wave energy along said structure propagating along said structure, and means for extracting from the region of said structure adjacent said source of energy traversing said periodic structure.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,534 Varian Aug. 5, 1952 2,4o9,694 Laidig Oct. 22, 1946 2,584,323 Berterottiere Feb. 5, 1952 2,617,961 Bruck Nov. 11, 1952 2,786,959 Warnecke et al Mar. 26, 1957 FOREIGN PATENTS 699,893 Great Britain Nov. 18, 1953 UNITED STATES PATENT OFFICE CER'I'IFICATE OF CORRECTION Patent No. 2,892,963 I o June 30, 1959 vEdward C, Dench It is hereby certified that error appears in the above numbered patent requiring correction ;and that the said Letters Patent lshould read as corrected below.,

In the' grant, lines l, l2 and 3, for Edward C., Denc'h, of Needham, .Massa- .chusetts," read Edward C., Dench, of Needham, Massachusetts, assignor to aytheon Company, a corporation of Delaware, line' 12, for "Edward C, Dench, his heirs" r'ead Raytheon Company, its successors in the heading to the printed specification, line 3, for "Edward Co Dench, Needham, Mass.,n

,read -z- Edward C. Dench, Needham, Mass., assig'nor to Raytheon Company, a cor- (SE-A1;)

poration of Delaware in the printed specification, ,column 5, line 41, after "inner-" insert periphery of c'ath'ode ll while the other' end, which may column 6, lines 14 and 15, for "compriees" read comprises w..

Signed .and sealed this 12th day of Apr-il 1960.;

.KABL'H XLINE ROBERT c. wATsoN Attestrng' Officer I p i Comnissoner of Patents UNITED STATES PATENT OFFICE CER'I'IFICATE OF CDRRECTION Patent Noe 2,8%,963 I June 30, 1959 Edward C Denoh It hereby Certified that error appears in the above numhered patent requiring correetion and that the said Letters Patent should read 'as oorrected below.,

` In the grant, lna's 1,,2' and 3, for Edward 0., Dencfh, of Needham, Massa chusetts' read ,wz Edward C Deneh, of Needham, Massachusetts, assignor to Raytheon Company, a Corporation of Delaware, w; line' 12, i'or "Edward C, Denoh, his heirs?i read w Raytheon Company, its sueeessors ImK; in the' heading to the' pr'inted specification, line' 3, `forV '*Edward 0a Denoh, Needham, Mass.,n

,read Edward C, Deneh, Nie'e'dham, Masso, assignor to Raytheon Company, a corn- I (stali) poration of Delaware w; in the printed specification, column 5, line ,41, after Winner." insert mperiphery of' e'athode' ll while the' other' end, which may 's-; oolumn', lines 14 and 15, for "oomprioe's" read oomprises ma Signed and sealed this 12th day of April 1960,

ICABZL'jHof AXLINE ROBERT c. wATsoN i A'btesting" Officer v Comissioner of Patents UNITED sTATEs PATNT OFFICE CERTIFICATE OF CORRECTION Patent' No, 2,8%,963 June 3a, 1959 Edward (30 Dench It hereby ccrtifis'd that error appears in the above numharcd patsnt requiring corrsction .and that the said Letters Patent should read as corre'cted below.,`

In the grant, lines l, 2 and 3, for "Edward C, Dsnch, of Nscdhafn, Massa .chusetts, read mz Edward C, Dsnch, of Needham, Massachusetts, assignor to Raytheon Company, a corporation of Delaware, wz-3 line' 12, for "Edward C,

I Dench, his heirs" read m Raythaon Company, its successors m1; in the haading;

to the printed specification, lina' 3, for Edward C., Danch, Needham, Massa read Edward G., Danch, Nscdham, Masso, assignor to Baythson Company, a corni (ani) p'oration of Delaware in the printcd specification, column 53 lina Al, after "inner" inssrt psriphcry of c'athode ll while the' other' and, which may -fl-'; column 6, linss 14 and 15, for ncompricejsn read comprisss w.,

Signsd ,and saalsd this lth day of April l90 Attest:

,KABL'H AXLNE ROBERT c. wATsoN ttes'blng' Officer Comnissioner of Patents 

